Manufacturing method of electroluminescence display apparatus

ABSTRACT

A supported glass substrate is placed with an element-forming surface thereof facing downward. A mother sealing substrate is placed on a support made of a quartz glass or the like. An ultraviolet-curing sealing resin is applied on the mother sealing substrate. After the glass substrate is aligned with the mother sealing substrate, the glass substrate is pressed toward the sealing substrate. The sealing resin is irradiated with ultraviolet light transmitted through the sealing substrate.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method for manufacturing anelectroluminescence display. More specifically, it relates to a methodfor manufacturing an electroluminescence display apparatus wherein asubstrate onto which an electroluminescence element is formed is sealedusing a sealing substrate.

2. Description of the Related Art

In recent years, display apparatuses employing electroluminescence (EL:Electroluminescence) elements have received widespread attention.

A typical EL element is configured by sequentially laminating, forexample, an anode comprising a transparent electrode such as ITO (IndiumTin Oxide), a hole transporting layer, an emissive layer and a cathodeon a transparent substrate. In such an EL element, holes injected fromthe anode and electrons injected from the cathode are recombined in theemissive layer so that organic molecules contained therein are excitedand then excitons are generated. Subsequently, the emissive layer emitslight in the deactivation process of the excitons and the light isemitted from the transparent anode to the outside through thetransparent substrate.

A typical display apparatus using an EL element as described above has asealing substrate to seal the transparent element substrate onto whichthe EL element is formed in order to prevent degradation of thecharacteristics of the EL element due to moisture in the EL element.More specifically, in such display apparatus, degradation incharacteristics of the EL element due to moisture in the EL element isavoided by bonding an element surface of the transparent elementsubstrate having the above-described element formed thereon with thesealing substrate made of, for example, metal. When these substrates arebonded, a sealing resin, for example, a resin in which are mixedbead-shaped glass fibers to create a spacer, is used to define a gapbetween the sealing substrate and the transparent element substrate ontowhich the EL element is formed. However, because the heat resistance oftypical EL element materials is low, it is not possible to ensure thatquality of an EL display apparatus will be maintained when a sealingresin requiring a high-temperature heat treatment is used to bond thetransparent element substrate with the sealing substrate.

In order to resolve this problem, it can be conceived to adopt a methodfor applying a sealing resin cured with ultraviolet light between thetransparent element substrate and the sealing substrate, and the sealingresin is irradiated with the ultraviolet light transmitted through thesealing substrate to bond the transparent element substrate and thesealing substrate. The use of the sealing resin cured with ultravioletlight or the like allows the transparent element substrate to be bondedwith the sealing substrate without exposing the EL element to elevatedtemperatures. Accordingly, it becomes possible to maintain adequatequality for an EL display apparatus.

Here it should be noted that because the sealing resin is irradiatedwith light emitted from a UV lamp on the transparent element substrateside of the device, not just the sealing resin, but also the EL elementand other components are exposed to the ultraviolet light during thecuring process. Therefore, although degradation in EL elementcharacteristics resulting from exposure to elevated temperatures can beprevented, there remains a possibility that characteristics can bedegraded due to short-time exposure to the ultraviolet irradiation.

SUMMARY OF THE INVENTION

The present invention, which was conceived in view of the situationdescribed above, therefore aims to appropriately seal a substrate ontowhich an EL element is formed while maintaining adequate quality of adisplay apparatus.

In order to achieve the above object, the present invention provide amethod for manufacturing an electroluminescence display apparatuscomprising steps of affixing an element substrate on which anelectroluminescence element is formed and a sealing substrate fixedlyplaced so as to oppose to an element-forming surface of said elementsubstrate via a sealing resin between the two substrates, pressing saidelement substrate toward said sealing substrate, and curing said sealingresin so as to bond said element substrate and said sealing substrate.

In another aspect of the present invention, said sealing resin may bemade of a light-curing resin such as an ultraviolet-curing resin.

In another aspect of the present invention, said sealing substrate madeof a light-transmissive material which transmits light for curing saidsealing resin such that the sealing resin is irradiated with the light.

In another aspect of the present invention, said sealing substrate madeof a light-transmissive material is placed and fixed on a support forthe sealing substrate which is also light transmissive. Light for curingthe sealing resin is then transmitted through said sealing substrate andsaid support for the sealing substrate to irradiate said sealing resin.

In another aspect of the present invention, light for curing the sealingresin is emitted from a light source, placed below said support for thesealing substrate, and transmitted through said sealing substrate andsaid support for the sealing substrate to irradiate said sealing resin.

According to these aspects, even in a case where, for example, thesealing resin is irradiated with the light transmitted through thesealing substrate for curing, it is possible to ensure that the lightrequired to cure the sealing resin is not blocked by a moving systembecause the sealing substrate side is fixed at the time of bonding. Ifthe sealing substrate side is movable, it will be necessary to installthe moving system on the sealing substrate side causing blockage of theirradiation with the lights to thereby facilitate effective irradiationof the sealing resin with light for curing. Further, because thestructure is not as complex as that which would be required if thesealing substrate were movable. As a result, it becomes possible toreduce manufacturing costs involved with the sealing process.

According to another aspect of the present invention, said elementsubstrate is affixed with said sealing substrate after said sealingresin is applied on a bonding surface of said sealing substrate at alocation corresponding to a location surrounding an element-formingregion of said element substrate.

Thus, the sealing substrate, applied the sealing resin at the locationsurrounding the element-forming surface and fixedly placed, is affixedwith the element substrate by pressing the element substrate toward thesealing substrate. When a light-curing resin is used as the sealingresin as described above, it is possible to affix the two substrates andthen bond them by curing the sealing resin placed between them whileemploying a simple structure.

In another aspect of the present invention, said sealing substrate,placed with the bonding surface thereof facing upwards when said sealingresin is applied, is installed on said sealing substrate support in sucha manner that the bonding surface continues to face upwards after thecompletion of applying of said sealing resin.

Because at least the bonding surface applied with the sealing resin isfixedly placed facing upwards as described above, it is possible toproperly bond and seal the sealing substrate and the element substratewhile the sealing resin applied in paste form is reliably prevented fromdripping, falling, or otherwise improperly moving away from the appliedposition due to gravity. Further, by transiting to the subsequentaffixing process in a state in which the surface coated with the sealingresin continues to face upwards, it becomes unnecessary to employ aprocess of turning over or flipping the sealing substrate or the like.This further contributes to a reduction in manufacturing costs.

Further, in another aspect of the present invention, a depression ispreformed on said bonding surface side of said sealing substrate, and adesiccant is applied in said depression. Because the bonding surfacefaces upward throughout this stage of manufacture, it is still possibleto proceed to the bonding process without changing the work surface,even with the desiccant thus applied on the bonding surface side. Thiscontributes to still further reduction in manufacturing costs. Further,it is also possible to prevent dropping or falling of the desiccant dueto flipping of the work surface before the desiccant coated in a pastedform is cured and adhered on the sealing substrate side.

Moreover, in another aspect of the present invention, an element layerto be formed by evaporation of said electroluminescence element providedon said element substrate is formed in a state that said element-formingsurface faces downwards.

According to this technique, a material is evaporated from anevaporation source provided in a lower location of the substrate andthen vapors of the material climbing up are adhered onto theundersurface of the substrate placed above the material. Thus, formationof the element layer by evaporation can be completed effectively.

In another aspect of the present invention, an element layer of saidelectroluminescence element is formed on said element substrate byevaporation in a state wherein said element-forming surface facesdownwards, and then said element substrate placed with saidelement-forming surface facing downwards is pressed to said sealingsubstrate immovably placed at the lower location so as to affix thesubstrates by the sealing resin located between them.

Thus, on the element substrate side, when the evaporation method isemployed to form the element layer, the element layer is formed in astate wherein the element-forming surface faces downwards. After this,the element substrate proceeds to the bonding process with theelement-forming surface still facing downward. This allows the elementsubstrate to be efficiently placed on the sealing substrate, in turnfixedly placed below the element substrate, without changing thedownward-facing work surface.

In another aspect of the present invention, at the affixing between saidelement substrate and said sealing substrate said sealing substrate isfixedly placed in such a manner that the surface to be bonded with saidelement substrate faces upward said element substrate is movably placedwith the element-forming surface facing downward, and then said elementsubstrate is pressed toward said sealing substrate.

Because the sealing substrate is fixed and the element substrate placedon the upper side is movable, this structure realizes advantage suchthat, when a light-curing resin is used as the sealing resin and lightfor curing the resin is transmitted through the sealing substrate toexpose the sealing resin, it is not necessary to provide a mechanism formoving the sealing substrate side such that light will be transmitted.As a result, the light irradiation is not blocked. Further, the elementsubstrate can be moved by a simple mechanism because a light-irradiationmechanism is not required on the element substrate side. Still further,because the bonding surface of the sealing substrate continues to faceupwards after the sealing resin is applied thereon as described above atthe time of bonding with the element substrate, simple structure,precise bonding, and reduced manufacturing costs can be obtained.

In another aspect of the present invention, said element substratemovably placed is aligned with said sealing substrate fixedly placed byadjusting a location of said element substrate with reference to saidsealing substrate prior to said bonding.

When the element substrate side is moved to align with the sealingsubstrate, it becomes possible to precisely and reliably perform thealignment, to improve the sealing accuracy, and to contribute toimprovement of the final quality of a display apparatus because it isunnecessary to move the sealing substrate coated with the sealing resinas described above.

In another aspect of the present invention, a driver circuit to drivesaid electroluminescence element is placed on a peripheral area of anelectroluminescence element forming region of said element substrate,and a transistor, used by said driver circuit, onto which alightshielding gate electrode is formed at a location close to saidsealing substrate than an active layer.

In some instances, such a driver circuit may be placed in the vicinityof the region applied the sealing resin or placed in such a manner as tooverlay the region applied the sealing resin, such that the drivercircuit part is exposed to the light from the sealing substrate sidewhen the light irradiated in order to cure the sealing resin. Even inthis case, however, because the lightshielding gate electrode is placedon the sealing substrate side as a transistor for the driver circuit ata location closer to said sealing substrate in comparison with an activelayer, it is possible to prevent that characteristics of the transistoris adversary affected by exposing, for example, the channel region inthe active layer on the location opposing to the gate electrode tolight.

In another aspect of the present invention, on said electroluminescenceelement formed on said element substrate, a lightshielding layer isformed at a location closer to said sealing substrate than a position ofan emissive element layer in such a manner that said emissive elementlayer is shielded from exposure to light emitted from said sealingsubstrate side for curing said sealing resin. In addition, thelightshielding layer may be comprise, for example, the electrode of theelectroluminescence element.

Because the lightproof layer comprising, for example, the electrode isplaced on the sealing substrate side as described above, the emissiveelement layer of the electroluminescence element or the like isprotected from exposure to the light, even when the light for curing thesealing resin is emitted from the sealing substrate side. As a result,an emissive element layer susceptible to degradation due to exposure tointense light, namely the electroluminescence element, can be protected.

In another aspect of the present invention provide a method formanufacturing an electroluminescence display apparatus comprising stepsof affixing a mother element substrate comprising a plurality of elementsubstrate regions on which are formed electroluminescence elements, witha sealing substrate applied a sealing resin in such a manner that eachdisplay region in said plurality of element substrate regions issurrounded with said sealing resin, pressing said mother elementsubstrate and sealing substrate affixed each other via said sealingresin, and said sealing resin is irradiated with light transmitted fromsaid sealing substrate side for curing so as to bond each of saidelement substrate forming regions of said mother element substrate withcorresponding regions of said sealing substrate.

The electroluminescence elements and the transistors for driving themformed on the mother element substrate side may sometimes block thelight. Therefore, it is impossible to irradiate the entire region of thesealing resin placed between the substrates with the light from themother element substrate side, even when a light-transmissive glasssubstrate is used as the mother element substrate. However, in manycases, it is not necessary to form such elements on the sealingsubstrate side. When the mother element substrate is bonded with thesealing substrate, the sealing resin can be cured over a widespread areauniformly and simultaneously by exposing the sealing resin to the lightemitted from the sealing substrate side in order to cure the sealingresin located between substrates.

In another aspect of the present invention, said mother elementsubstrate, movably placed with element-forming surface thereof facingdownward, is pressed toward said sealing substrate, fixedly placed insuch a manner that the surface to be bonded with said mother elementsubstrate faces upward at the time of affixing.

In another aspect of the present invention, said mother elementsubstrate movably placed is aligned with said sealing substrate fixedlyplaced by adjusting the location of said mother element substrate withreference to said sealing substrate prior to said bonding.

In another aspect of the present invention, light from saidelectroluminescence elements is emitted toward the outside from theelement substrate side located on the other side of said sealingsubstrate.

When mother element substrate is bonded with the sealing substrate asdescribed above, it becomes possible to execute sealing procedure usinga simple mechanism by fixedly placing the sealing substrate in such amanner that the surface applied with the sealing resin faces upward, byproviding the moving system to the mother element substrate placed abovethe sealing substrate at the time of bonding or at the time ofalignment.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of an active matrix type EL display apparatusaccording to an embodiment of the present invention.

FIGS. 2A and 2B are views along line D—D and line E—E in FIG. 1,respectively.

FIG. 3 is a conceptual illustration of the EL display apparatusaccording to the embodiment of the present invention as viewed fromabove.

FIG. 4 is a flowchart showing process steps of a method formanufacturing an EL display apparatus in accordance with the embodimentof the present invention.

FIG. 5 is a conceptual illustration of a state of a glass substrate inaccordance with the embodiment of the present invention.

FIG. 6 is another conceptual illustration of a state of a sealingsubstrate in accordance with the embodiment of the present invention.

FIG. 7 is a sectional schematic showing states of a bonding process forbonding the glass substrate with the sealing substrate in themanufacturing method according to the embodiment of the presentinvention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

A method for manufacturing an electroluminescence display according tothe present invention will be described below, using an example methodfor manufacturing an active matrix type electroluminescence display andwhile referring to the drawings.

FIG. 1 is a plan view of an EL element (which is an organic EL elementin this embodiment and is indicated as “EL” in FIG. 1) and itsperipheral section, of an EL display apparatus to be manufacturedaccording to the present embodiment. Referring to FIG. 1, the EL displayapparatus comprises a display pixel formed by the EL element, and a thinfilm transistor (TFT) which is an active element provided for eachcorresponding display dot.

More specifically, as shown in FIG. 1, gate signal lines GL and drainsignal lines (data signal lines) DL are arranged in a matrix as signallines for performing drive control of the EL element. An EL element(display pixel) is provided corresponding to each intersection of thesesignal lines. In the EL display apparatus shown in FIG. 1, each displaypixel corresponds to any one of the primary colors R, G and B, tothereby enable color image display.

Additional elements are also provided so as to perform drive control ofeach of the EL elements separately. First, near the above-describedintersection of the signal lines, a thin film transistor (TFT1), whichis connected with the gate signal line GL and functions as a switchingelement to be turned ON due to the activity of the gate signal line GL,is formed. A source S1 of this TFT1 serves also as a capacitor electrodeCE and a storage capacitor is formed between the capacitor electrode CEand a capacitor line CL made of a refractory metal such as chromium (Cr)and molybdenum (Mo). When the TFT1 is turned ON, an electrical charge inaccordance with the voltage of a data signal supplied from the data lineDL is accumulated in the storage capacitor.

The capacitor electrode CE is connected to a gate G2 of a thin filmtransistor (TFT2) which drives the EL element. Further, a source S2 ofthe TFT2 is connected with a transparent electrode 11 which is an anodeof the EL element, while a drain D2 of the TFT2 is connected with adrive power source line IL which is a current source for supplying anelectrical current to the EL element. With this structure, a voltage inaccordance with the electrical charge stored in the storage capacitor isapplied from the capacitor electrode CE to the gate G2, such that acurrent in accordance with the applied voltage is supplied from thedrive power source line IL to the EL element.

FIGS. 2A and 2B are cross sectional views taken along lines D—D and E—Eof FIG. 1, respectively. As shown in FIGS. 2A and 2B, theabove-described EL display apparatus is formed by sequentially forming athin film transistor and an EL element on a glass substrate 1 in alaminated structure.

First, the TFT1 which serves as a switching transistor for performingcharging control of the storage capacitor is formed in a manner shown inFIG. 2A. Specifically, on the glass substrate 1, a poly-silicon layer 2is formed. In this poly-silicon layer 2, the above-described source S1and the drain D1 as well as channels Ch1 are formed, while LDDs (LightlyDoped Drains) are further provided on both outer sides of the channelsCh1. The poly-silicon layer 2 also serves as a storage capacitorelectrode CE. On the poly-silicon layer 2 and the storage capacitorelectrode CE, a gate insulating film 3, the above-described gate signalline GL made of a refractory metal such as Cr and Mo and a gateelectrode G1 which is integral with the gate signal line GL, and astorage capacitor electrode line CL are formed. Further, over theselayers, an interlayer insulating film 4 formed by accumulating a siliconoxide film and silicon nitride film, in this order, in a laminatestructure is provided. This interlayer insulating film 4 has an openingat a position corresponding to the drain D1. By filling this openingwith a conductive material such as aluminum, the drain D1 comes intoelectrical contact with the drain signal line DL. Further, on thesedrain signal line DL and the interlayer insulating film 4, aplanarization insulating film 5 made of, for example, an organic resin,is formed for surface planarization.

On the other hand, the TFT2 for driving the EL element is formed in amanner as shown in FIG. 2B. Specifically, on the glass substrate 1, apoly-silicon layer 2 which is equal to that shown in FIG. 2A is formed.In this poly-silicon layer 2, a channel Ch2, a source S2, and a drain D2of the TFT2 are formed. On this poly-silicon layer 2, a gate insulatingfilm 3 which is equal to that shown in FIG. 2A is formed, and on theportion of the gate insulating film 3 which is located above the channelCh2, a gate G2 made of a refractory metal such as chromium (Cr) andmolybdenum (Mo) is provided. Over the gate G2 and the gate insulatingfilm 3, an interlayer insulating film 4 and a planarization insulatingfilm 5 which are equal to those shown in FIG. 2A are sequentially formedin a laminate structure. The interlayer insulating film 4 has an openingat a position corresponding to the drain D2, and by filling this openingwith an conductive material such as aluminum, the drain D2 comes inelectrical contact with the drive power source line IL. Also, a contacthole is formed through portions of the interlayer insulating film 4 andthe planarization insulating film 5 which correspond to the source S2.Then, ITO (Indium Tin Oxide) is formed so as to fill this contact hole,so that the source S2 comes in electrical contact with an transparentelectrode 11 made of ITO or the like. The transparent electrode 11constitutes an anode of the EL element. It should be noted that thesource S2 is not necessarily brought in direct contact with the ITO, andthe source S2 and the ITO may be connected in the following manner, forexample. That is, a contact hole is first formed in the interlayerinsulating film 4 and the gate insulating film 3, and the hole is filledwith a conductive material such as aluminum simultaneously with theformation of the contact (the drain electrode) between the drain D2 andthe power source line IL. Then, another contact hole is formed at acorresponding portion of the planarization insulating film 5, which issubsequently formed, and ITO is formed so as to fill this contact hole.

As an example, the EL element may comprise the following layerssequentially accumulated in a laminate structure:

-   -   a) a transparent electrode 11;    -   b) a hole transporting layer 12 made of NBP;    -   c) an emissive layer 13 for red (R) obtained by doping a dopant        of red color (DCJTB) into a host material (Alq3), for green (G)        obtained by doping a dopant of green color (Coumarin 6) into a        host material (Alq3), or for blue (B) obtained by doping a        dopant of blue color (Perylen) into a host material (BAlq);    -   d) an electron transporting layer 14 made of Alq3;    -   e) an electron injecting layer 15 made of lithium fluoride        (LiF); and    -   f) an electrode (cathode) 16 made of aluminum (Al).

The abbreviations used in the above description refer to the followingmaterials:

-   -   “NBP” refers to        N,N′-di((naphthalene-1-yl)-N,N′-diphenylbenzidine);    -   “Alq3” refers to tris(8-hydroxyquinolinato)aluminum;    -   “DCJTB” refers to        (2-(1,1-dimethylethyl)-6-(2-(2,3,6,7-tetrahydro-1,1,7,7-tetramethyl-1H,5H-benzo[ij]quinolizin-9-yl)ethenyl)-4H-pyran-4-ylidene)propanedinitrile;    -   “Coumarin 6” refers to        “3-(2-benzothiazolyl)-7-(diethylamino)coumarin; and    -   “BAlq” refers to        (1,1′-bisphenyl-4-Olato)bis(2-methyl-8-quinolinplate-N1,08)Aluminum.

The hole transporting layer 12, the electron transporting layer 14, theelectron injecting layer 15 and the electrode 16 are also formed in theregions shown in FIG. 2A as common layers. However, the emissive layer13, which is formed in an individual island shape for each pixel so asto correspond to the transparent electrode 11, is not shown in FIG. 2A.It should be noted that, as shown in FIGS. 2A and 2B, an insulating film10 is formed on the planarization insulating film 5.

Further, in order to keep the EL element formed on the glass substrate 1from contacting with water, the EL element-forming surface (elementsurface) of the glass substrate 1 is sealed by a sealing substrate 30made of glass as well as a desiccant 31 comprising, for example, acalcium oxide (CaOx), a barium oxide (BaOx) and so on is includedbetween the sealing substrate 30 and a cathode 16.

FIG. 3 is a conceptual illustration showing the glass substrate 1 fromthe upper surface thereof (the element-forming surface, the side sealedby the sealing substrate 30). On the glass substrate 1, a display regionDP having the above-mentioned EL element and the TFT, and drivers Dv andDh to drive the TFT in the display region DP are formed as shown in FIG.3.

The display region DP is sealed by the sealing substrate 30 in order tokeep the EL element formed within the display region from contactingwith water. To be more specific, the glass substrate 1 and the sealingsubstrate 30 are bonded with each other by a sealing resin 40 coated insuch a manner as to surround the display region DP. This sealing resin40 may contain, for example, glass fibers (not shown in the figure) inthe shape of a bead to define a gap between the glass substrate 1 andthe sealing substrate 30. The sealing substrate 30 has a depressionformed on the region corresponding to the display region DP where thedesiccant 31 is filled.

Referring to FIG. 4, a method for manufacturing an EL display apparatusin accordance with this embodiment will be explained. FIG. 4 showsprocess steps for manufacturing an EL display apparatus in accordancewith the embodiment. In this embodiment, plural sets of the displayregions DP and the drivers Dv and Dh as shown in FIG. 3 are formed on asingle sheet of a large glass substrate in order to produce a pluralityof EL display apparatuses at a time. As shown in FIG. 5 in detail,sixteen sheets of the display region DP's and sixteen sets of drivers Dvand Dh (not illustrated) are formed on a glass substrate 1L in thisembodiment.

Referring again to FIG. 4, the TFTs, the transparent electrodes 11, andso on are formed on the glass substrate 1L in the manner shown in FIGS.2A and 2B (S100). At the same time, the drivers Dv and Dh are formed inregions surrounding the display region DP's on the glass substrate 1L.

Next, the hole transporting layer 12 of the EL element is formed byvacuum evaporation (S101). The hole transporting layer 12 does not coverforming regions of the drivers Dv and Dh and not-illustrated terminalslocated outside of the display regions DP of FIG. 3 and terminals (alsonot illustrated), but only covers the display regions DP even in a casewhere the hole transporting layer 12 is formed in common to all thepixels as shown in FIGS. 2A and 2B. Therefore, at least when a pluralityof panels are produced from a single-sheet substrate as shown in FIG. 5,a mask having openings only for the display regions DP is used forforming the hole transporting layer 12. In this case, the mask is presetin a vacuum chamber for forming the hole transporting layer. The glasssubstrate 1L, onto which the planarization insulating film 10 is formedby overlaying the edge of the transparent electrode 11, is inserted intothe vacuum chamber from above with its upper surface facing down andaligned with the mask laid beneath the substrate. After completion ofalignment, a material of the hole transporting layer is evaporated froman evaporation source provided under the mask so that the holetransporting layer is formed on each of the display regions.

Next, the emissive layer 13 is formed by vacuum evaporation on the glasssubstrate 1L having the hole transporting layer 12 formed as describedabove without exposing the glass substrate 1L to air (S102). At the timeof forming the emissive layer 13, the glass substrate 1L is insertedinto a vacuum chamber, in which a mask having an opening correspondingto the transparent electrode 11 formed on the glass substrate 1L ispreset, from above the mask. Then, the glass substrate 1L placed withits element-forming surface facing downward is aligned with the mask.After completion of alignment, a material of the emissive layer 13 isheated and evaporated through the opening of the mask so that theemissive layer 13 is formed on the glass substrate 1L. Referring to theformation of the emissive layer 13 by evaporation in detail, for primarycolors of red (R), green (G), and blue (B), respective masks and vacuumchambers are prepared and used for forming the emissive layer 13.

The glass substrate 1L having the emissive layer 13 thus formed thereonis removed from the vacuum chambers used for forming the emissive layer.Successively, the electron transporting layer 14, the electron injectinglayer 15, and the cathode 16 are formed by the same type of vacuumevaporation, also in a state in which the surface, where the emissivelayer 13 is formed, faces downward vertically (S103). For the electrontransporting layer 14, there may be cases where at this point theelectron transporting layer 14 is formed in individual patternscorresponding to each pixel using a similar mask just as with theemissive layer 13 depending on characteristics of organic materials tobe used. On the other hand, the electron injecting layer 15 and thecathode 16 are formed, as in the case of the hole transporting layer 12described above, in a pattern overlaying all of the display regions DPwithout covering the surrounding regions where the drivers Dv and Dh arelocated.

Referring to the sealing substrate 30, a depression to be filled withthe desiccant 31 is formed thereon (S200). More precisely, in thisexample sixteen sets of the sealing substrates 30 are simultaneouslyformed on the mother sealing substrate 30L to be bonded with the glasssubstrate 1L as shown in FIG. 6. Therefore, sixteen parts of depressions30 h are formed on the mother sealing substrate 30L. The depressions 30h are formed on the mother sealing substrate 30L in the regionscorresponding to the display regions DP of the glass substrate 1L.

After forming the depressions 30 h on the mother sealing substrate 30L,the desiccant 31 is applied in the depressions 30 h as shown in FIG.6(b) (S201 shown in FIG. 4). After the completion of the applying andcalcining of the desiccant 31, the sealing resin 40 is applied aroundeach of the above-mentioned depressions 30 h on the mother sealingsubstrate 30L (S202 shown in FIG. 4). In order to define the gap betweenthe glass substrate 1L and the mother sealing substrate 30L, the sealingresin 40 contains glass fibers, as described above.

When the processes for forming the cathode 16 on the organic layer ofthe EL element formed over glass substrate 1L and for applying thesealing resin 40 on the mother sealing substrate 30L are completed, theglass substrate 1L is affixed to the mother sealing substrate 30L (S300shown in FIG. 4).

Because organic EL elements which have already developed do not havehigh heat resistance, as described above, there is a possibility ofdegradation of the EL element when a thermosetting resin is used as thesealing resin. In order to prevent the possibility, in the presentinvention, an epoxy resin, for example, a resin capable of cationicpolymerization, which is cured by exposure to ultraviolet light is usedas the sealing resin 40. Thus, by curing the sealing resin 40 byexposing it to ultraviolet light, the glass substrate 1L can be bondedwith the mother sealing substrate 30L while degradation incharacteristics caused by exposing the EL element to elevatedtemperatures is prevented.

However, application of ultraviolet light to the sealing resin 40through the glass substrate 1L creates, as noted above, a risk thatother components whose characteristics may be prone to degradation whenexposed to ultraviolet light (specifically, for example, an organiclayer using organic materials of which glass-transition temperature Tgis low) such as the hole transporting layer 12, the emissive layer 13,the electron transporting layer 14, the electron injecting layer 15, andso on among EL elements.

Therefore, in this embodiment, a substrate allowing ultraviolet light totransmit is used as the mother sealing substrate 30L and the sealingresin 40 is irradiated with the ultraviolet light transmitted throughthe mother sealing substrate 30L. By thus applying ultraviolet lightfrom the mother sealing substrate 30L side, the cathode 16 shown in FIG.1 protects the components whose characteristics are prone to degradationwhen exposed to ultraviolet light, such as the above-noted holetransporting layer 12, the emissive layer 13, the electron transportinglayer 14, the electron injecting layer 15, and so on among EL elements,from exposure to the ultraviolet light. In this embodiment, glass isused as the mother sealing substrate 30L allowing the ultraviolet lightto transmitted.

Further, in this embodiment, transistors having top gate structure areused as the transistors which form the drivers Dv and Dh shown in FIG. 3and materials opaque to ultraviolet light are employed as gate materialsof the transistors. Regarding the TFT in the pixel part shown in FIGS.1, 2A and 2B, because it is usually formed in almost the same processand at the same time as the transistors of the drivers Dv and Dh, thetop gate structure is also applied to the TFT.

There is a possibility that the characteristics of transistors usingpolycrystalline silicon or the like as an active layer will vary whenchannel regions of the transistors are irradiated with ultravioletlight. It is inevitable that the region, in particular, where thedrivers Dv and Dh are formed thereon will be exposed to the ultravioletlight used for curing the sealing resin because the region where thedrivers Dv and Dh are formed overlaps the region where the sealing resinis coated. If the drivers Dv and Dh are formed on regions where thesealing resin is not applied in addition to shielding the regions wherethe drivers Dv and Dh are formed thereon from ultraviolet irradiation,edge portions of ineffective regions which do not have the function of adisplay operation as the EL display apparatus will be increased. Inaddition to this, the number of manufacturing process steps will beincreased because a mask for shielding the drivers Dv and Dh fromultraviolet irradiation is used at the time of the ultravioletirradiation.

In contrast to the transistors described above, here the transistors inthe drivers Dv and Dh are formed as top gate transistors. Accordingly,because the gate protects the channel region from exposure toultraviolet irradiation, it becomes possible to prevent change in thecharacteristics of the transistors due to direct irradiation withultraviolet light to the channel region.

Further, in this embodiment, the surface of the glass substrate 1L onwhich the surface where the EL elements are formed and which facesdownward and is affixed and bonded to the surface of the mother sealingsubstrate 30L where the desiccant 31 is applied and which faces upward.More specifically, all of the emissive layer 13, the electrontransporting layer 14, the electron injecting layer 15, and the metalelectrode 16 are formed on the hole transporting layer using organicmaterials by vacuum evaporation on the glass substrate 1L in theprocesses preceding the affixing process, as shown in FIG. 4. In thefilm forming process according to the vacuum evaporation, the glasssubstrate 1L is placed in such a manner that the element-forming surfacethereof faces down. On the other hand, on the mother sealing substrate30L, the desiccant 31 in a paste form is applied and calcined, and theseal resin 40 is applied and maintains its paste form. After that, themother sealing substrate 30L advances to the subsequent sealing process.Therefore, the mother sealing substrate 30L is processed in a state thatthe surface wherein the desiccant 31 and the sealing resin 40 areapplied faces upward in order to avoid falling off of the desiccant 31and the sealing resin 40 before curing. According to this embodiment,the glass substrate 1L placed with its element-forming surface facingdownward is affixed with the mother sealing substrate 30L placed withits surface applied the sealing resin 40 facing up. Thus, neithersubstrate requires flipping before proceeding to the affixing process.In other words, both substrates can easily advance to the affixingprocess.

When the glass substrate 1L is affixed with the mother sealing substrate30L, pressure is applied in order to securely bond these substrates. Inthe present embodiment, the pressure is applied as shown in FIG. 7, by apressing system (not illustrated), to the glass substrate 1L from itsupper surface (where the EL elements are not formed) toward the mothersealing substrate 30L placed on a transparent support 50 which allowsthe ultraviolet light to transmit. This creates a necessity forinstalling a UV lamp on the support 50 side because ultraviolet light isirradiated from the support 50 side through the mother sealing substrate30L. The mother sealing substrate 30L, however, need not be providedwith a pressing system because of the pressing system installed on theglass substrate 1L side. Thus, the support 50 need only hold the mothersealing substrate 30L and transmit the light emitted from the UV lamp.This allows for simplification of the mechanism on the side of thesupport 50. Further, the bonding (sealing) process can be completedeasily without developing additional constraints such that theultraviolet light be blocked by components of the pressing system,because the pressure is not applied from the support side. The alignmentposition at the time of affixing is adjusted on the glass substrate 1Lby moving a support 51 which holds the glass substrate 1L. Therefore,the mother sealing substrate 30L can be fixedly placed on the support50. If it is intended that the mother sealing substrate 30L be movable,the mother sealing substrate 30L should be tightly held on the support50 by absorption or the like. In order to absorb the mother sealingsubstrate 30L, it is necessary to bore holes for absorption in thesupport 50. Such openings of the holes are prone to cause scattering ofUV light emitted from the lamp. The scattering can interfere witheffective curing of the seal resin. However, the absorption and holdingof the mother sealing substrate 30L are not necessary in thisembodiment. Therefore, problems as described above do not arise.

Referring to FIG. 7, the bonding process of the glass substrate 1L andthe mother sealing substrate 30L is described in detail below.

FIG. 7(a) shows that the mother sealing substrate 30L is placed on thesupport 50 made of, for example, quartz glass which allows ultravioletlight to transmit and above these the glass substrate 1L is held on thesupport 51 by, for example, vacuum suction. The glass substrate 1L isaligned with the mother sealing substrate 30L with reference to analignment mark 1 a such as a mark of FIG. 5 formed on the glasssubstrate 1L and an alignment mark 30 a such as a mark of FIG. 6 formedon the mother sealing substrate 30L. That is, while positions of thealignment marks 1 a and 30 a are monitored by, for example, a CCD(Charge Coupled Device) camera 52 shown in FIG. 7(a), the support 51 isshifted to the location where the alignment mark 1 a is matched to thealignment mark 30 a so as to align the glass substrate 1L with themother sealing substrate 30L.

After the glass substrate 1L and the mother sealing substrate 30L havebeen aligned, the glass substrate 1L is bonded with the mother sealingsubstrate 30L. To be more specific, the glass substrate 1L is lifteddown toward the mother sealing substrate 30L so that the lower surfaceof the glass substrate 1L makes contact with the sealing resin 40applied on the sealing positions of the mother sealing substrate 30L.After the contact is made, the glass substrate 1L is further pressedtoward the mother sealing substrate 30L from the support 51 side untilthe gap between the glass substrate 1L and the mother sealing substrate30L reaches the size defined by a glass fiber 40 s contained in thesealing resin 40. Whether the specified gap size is obtained isdetermined based on, for example, determination as to whether or not thepressure applied to the glass substrate 1L by a pressing componentreaches or exceeds a predetermined magnitude. Once the gap between theglass substrate 1L and the mother sealing substrate 30L reaches thespecified size, the UV lamp installed in a lower place of the support 50is turned on so that the sealing resin 40 is irradiated with ultravioletlight (indicated as UV in FIG. 7(a)) transmitted through the transparentsupport 50 and the mother sealing substrate 30L. As a result, thesealing resin 40 made of ultraviolet-curing resin is cured.

FIG. 7(b) shows the display region DP irradiated with the ultravioletlight emitted from the mother sealing substrate 30L side. The metalelectrode (cathode) 16 covering the whole display region DP is formed atthe top layer of the EL element in the display region DP. Because thecathode 16 made of aluminum or the like blocks the ultravioletirradiation, the EL elements (particularly organic layers) and thetransistors formed under the cathode 16 in the display region DP areprotected from exposure to ultraviolet light. In FIG. 7(c), thetransistors in the drivers Dv and Dh irradiated with the ultravioletlight are shown. In contrast to the display region DP, the lightproofcathode 16 is not formed at an upper layer in the drivers Dv and Dh, asshown in FIG. 7(c). The transistors, however, have the top gatestructure. A gate electrode 60 g protects the channel region 60 c fromultraviolet irradiation (indicated by solid lines with an arrow in FIG.7(c)).

According to the present embodiment as described above, followingadvantages are obtained:

-   (1) The sealing resin 40 is irradiated with ultraviolet light    emitted from the mother sealing substrate 30L side for curing in    order to bond the glass substrate 1L with the mother sealing    substrate 30L. If the ultraviolet light is emitted from the glass    substrate 1L side, the organic layers of the EL element in the    display region DP will be irradiated with the ultraviolet light,    raising the possibility of degradation in characteristics of the EL    element. However, when the ultraviolet light is emitted from the    mother sealing substrate 30L side, the cathode 16 protects the EL    element from exposure to the ultraviolet light. This prevents    degradation of the organic layers due to exposure to the ultraviolet    light.-   (2) Through the use of the transistors having the top gate structure    as the transistors for the drivers Dv and Dh, the gate electrode    protects the channel region of the transistors in the drivers Dv and    Dh from exposure to the ultraviolet light without installation of    any additional opaque components.-   (3) Application of the pressure from the glass substrate 1L side at    the time of bonding precludes constraints of pressing so as not to    block the ultraviolet light. As a result, the bonding procedure is    simplified. Further, when the glass substrate 1L is aligned with the    mother sealing substrate 30L at the time of bonding, the glass    substrate 1L side is shifted. This means that irradiation with the    ultraviolet light emitted from the mother sealing substrate 30L side    is not blocked by movements for shifting the mother sealing    substrate 30L and for suctioning the mother sealing substrate 30L in    order to tightly hold the mother sealing substrate 30L at shifting.-   (4) The glass substrate 1L is placed with the EL element-forming    surface thereof facing downward and the mother sealing substrate 30L    is placed with the surface thereof applied with desiccant 31 and the    sealing resin 40 facing upward direction when they are bonded. This    placement eliminates any necessity for flipping the either substrate    before bonding. Accordingly, the transition to the bonding process    from the previous process can be easily and quickly completed.

The above-described embodiment may be varied without departing from thespirit of the present invention or the scope of the subjoined claims.

For example, the glass substrate 1L and the mother sealing substrate 30Lare not limited to substrates on which sixteen display panels are formedsimultaneously as exemplified in the above embodiment, but any arbitraryappropriate number of one or more display panels may be formed thereon.

The transistors for driving the EL element formed in the display regionDP are not limited to those having the top gate structure as shown inFIG. 1 but may have a bottom gate structure or the like. Morespecifically, because the top layer (the mother sealing substrate 30Lside) of the display region DP on the glass substrate 1L is covered withthe cathode 16 as described above, the cathode 16 protects the inside ofthe display region DP from exposure to ultraviolet light. For thisreason, there is no possibility that the channel regions of thetransistors within the display region DP will be irradiated withultraviolet light. However, when the electrode 16 is formed so as tocorrespond to the transparent electrode 11, it is preferable that thetransistors within the display region DP have a top gate structure andare formed using gate materials capable of blocking ultraviolet light.

The EL display apparatus is not limited to those described above but mayhave a structure in which, for example, a source of the transistor isconnected to the cathode instead of the anode. Further, the structure isnot limited to the active matrix type. For example, a passive matrixstructure may be employed as long as EL element electrodes on thesealing substrate side formed on the glass substrate are made ofmaterials capable of blocking the ultraviolet light. In such a case, thepresent invention in which the sealing resin is irradiated with theultraviolet light from the sealing substrate side for bonding may alsobe effectively applied.

At the time of bonding, it is not necessary to place the glass substrate1L in such a manner that the bonding surface thereof matches the bondingsurface of the mother sealing substrate 30L in a parallel directionwhile the glass substrate 1L is located above the sealing substrate 30.That is, the essential point is that the glass substrate 1L side ismoved to perform alignment under the condition that the location of themother sealing substrate 30L is fixed as well as pressure is applied ina direction toward the mother sealing substrate 30L side. As long asthis is maintained, it is possible to have the structure such that thework surfaces of both of the substrates are slightly tilted to eachother with reference to the parallel direction or the work surfaces ofboth of the substrates match in the vertical direction. In anystructure, it is possible to align both of the substrates and applypressure to them without blocking irradiation with the ultraviolet lightand bonding can be completed with a simple structure.

The processes preceding to the bonding of the glass substrate 1L and themother sealing substrate 30L are not limited to the series of processesof S101 to S103 and S200 to S202 listed in FIG. 4, but it is possible tomake modifications that, for example, the sealing resin is applied tothe glass substrate side as required. Further, the formation of ELmaterials using a mask by vacuum evaporation is not limited in itsapplication to the emissive layer. For example, when the holetransporting layer 12, electron transporting layer 14 and/or electroninjecting layer 15 are formed so as to vary in thickness of film fromone primary color to another, these layers may be formed by similartechnique using the mask, similarly to the case with a emissive layer.

The material of the mother sealing substrate 30L is not limited toglass. Any suitable material which allows ultraviolet light to transmit,such as a transparent resin or the like, may be used for the mothersealing substrate 30L.

Although an example sealing resin having a property of being curablewith ultraviolet light is utilized in the embodiment and modificationsdescribed above, the present invention is not limited to use of such aresin. Any resin having a property of being curable with an appropriatewavelength of light which does not cause a temperature increase in theEL element may be used as the sealing resin. In such a case, the lightshould still be irradiated to the sealing resin through the sealingsubstrate, which therefore must allow that frequency of light totransmit. At that point, members having capability of blocking theultraviolet light such as the gate electrodes or the like described inthe embodiment should be replaced with elements blocking the appropriatewavelength of light.

Materials of the EL elements are not limited to those listed above. Itis possible to use materials having electroluminescence capability,electric charge transporting capability, and capability of providing anelectron and hole necessary for an electrode. These materials may bethose known already or those which will be developed in future, and canbe used singly or in combination.

In the example illustrating the embodiment, the cathode 16 formed in thetop layer of the EL element is also formed by vacuum evaporation withthe cathode forming surface facing down as is the case with formingother organic layers. However, the cathode 16 may be formed bysputtering or another method as appropriate to the material used for theelectrodes. When the formation is performed by sputtering or the like,it is desirable that cathode materials are laminated with thecathode-forming surface facing upwards, in contrast to formation byvacuum evaporation. That is, in the process preceding to bonding of theglass substrate 1L and the mother sealing substrate 30L, the mothersealing substrate 30L is placed with the bonding surface facing upwardsas described above and the glass substrate 1L is also placed with thebonding surface facing up, which is opposite to the state describedabove. It is in such a case necessary that one of the two substrates beflipped over in order to bond the substrates. In order to prevent theuncured sealing resin 40 applied on the upper surface of the mothersealing substrate 30L from dripping or falling before affixing, it is insuch a case further preferable that mother sealing substrate 30L theglass substrate 1L, and not the mother sealing substrate 30L, be turnedupside down before proceeding to the affixing process. In addition, itis necessary that the ultraviolet light to cure the sealing resin 40 beapplied through the transparent support 50 and the mother sealingsubstrate 30L. If the support 50 is installed with mechanisms for movingand/or absorbing the mother sealing substrate 30L, the likelihood thatthe ultraviolet light will interfere with these mechanisms will be high.As a result, mechanisms designed specifically to avoid the interferenceof the ultraviolet light are required. However, interference with theultraviolet light can be avoided by flipping over the bonding surface ofthe glass substrate 1L side so that it will face downward and thenpressing the mother sealing substrate 30L from the glass substrate 1Lside.

1. A method for manufacturing an electroluminescence display apparatuscomprising stops of: affixing an element substrate on which anelectroluminescence element is formed and a sealing substrate fixedlyplaced so as to oppose an element-forming surface of said elementsubstrate via a sealing resin between the two substrates; pressing saidelement substrate toward fixedly placed said sealing substrate; andcuring said sealing resin so as to bond said element substrate and saidsealing substrate, wherein: said element substrate is affixed with saidsealing substrate after said sealing resin is applied on bonding surfaceof said sealing substrate at a location corresponding a locationsurrounding an element-forming region of said element substrate; saidsealing substrate, placed with the bonding surface thereof facingupwards when said sealing resin is applied, is installed on said supportfor the sealing substrate in such a manner that the bonding surfacecontinues to face upwards after the completion of applying of saidsealing resin; a depression is preformed on said bonding surface side ofsaid sealing substrate; and a desiccant is applied in said depression ofthe sealing substrate.